Ag Nanoparticles Supported on Yttria-Stabilized Zirconia: A Synergistic System within Redox Environments

Journal Article · 18 February 2016 · Journal of Physical Chemistry. C

DOI: https://doi.org/10.1021/acs.jpcc.6b00189 · OSTI ID:1477742

Zhao, Zhouying ^[1]; Rossi, V. A. Vulcano ^[1]; Baltrus, John P. ^[2]; Ohodnicki, Paul R. ^[2]; Carpenter, Michael A. ^[1]

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1. SUNY Polytechnic Institute, Albany, NY (United States)
2. National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)

In this paper, we report a distinctive dynamic sintering-free redox behavior of Ag nanoparticles (AgNPs) on 30 nm thick yttria-stabilized zirconia (YSZ) films. The material system demonstrates reversible 200 nm shifts in the plasmonic spectra with an unprecedented particle phase/size/morphology oscillation during cyclic redox reactions in air and hydrogen/air at 300–400 °C. This is in significant contrast to the minor changes more commonly observed for AgNPs on quartz. It was found that the ionically active YSZ has a strong tendency to drive AgNPs to oxidize under oxidizing conditions, and upon surface oxidation a large differential surface energy is built up, forcing the core/shell particles to migrate and coalesce toward a lower system free energy. Most strikingly, once switched to a mixture of H₂ and air, the previously formed large dewetted metal-core/thick oxide-shell particles collapse, and new small Ag nanoparticles quickly form and remain in a highly dispersed and sintering-free state on YSZ. This is found to likely be due to catalytic production of water over the material system, which plays a key role in the dynamic redox activities. It is hypothesized that the small metallic particle regeneration and sinter-free behavior take place through a four-step process resulting from the synergistic behavior of AgNPs supported on YSZ within a redox environment: (I) production of a local humid environment via catalytic reactions of H₂ and O₂ mostly at the triple-phase boundary, (II) dissolution of Ag⁺ from both reduced Ag and the AgO_x shell, (III) collapse and spillover of the AgO_x shell/water layer with Ag ions onto the hydrous YSZ surface, and (IV) reduction, diffusion, nucleation, and growth to new small metallic AgNPs with a dynamic equilibrium quickly reached. As a result, the findings behind this novel system could set up an avenue for a new concept of catalysts operating in a self-controlled dynamic regime for governing chemical reactions via metal and ceramic synergized catalysis with high activities and stabilities.

• Research Organization: National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: FE0007190
• OSTI ID: 1477742
• Journal Information: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 9 Vol. 120; ISSN 1932-7447
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English